Final answer:
The trapped air in egg whites expands when heated, aiding in the foaming process, then the albumin protein unfolds and aggregates into a disorganized solid as the egg whites are cooked, a process which is irreversible and spontaneous above 373 K.
Step-by-step explanation:
When egg whites are subjected to heat, the air trapped within expands. This is because as the temperature increases, the molecules of air move faster and push against each other, causing the volume of the air to increase. This expansion aids in the creation of a foam during processes such as beating egg whites to make meringues. As heat is continually applied, the major component of egg white, which is albumin, unfolds from its compact, ordered structure due to the breaking of hydrogen bonds, requiring an input of energy (AH> 0). This eventually leads to the molecules aggregating into a disorganized solid state (AS > 0), as seen when egg whites are cooked and become solid. This process is irreversible and spontaneous at temperatures greater than 373 K, where the TAS term is dominant, and Gibbs free energy (AG) is negative (AG < 0), confirming the solidification of egg white as an eggs are hard-boiled.